The invention relates to a picking device for the picking motion of a loom, which generally is a shuttle. The picking device includes a spring for delivering picking energy to a pivot arm wherein the spring is adapted to be tensioned by way of a cam drive.
In looms having more than 6 m product width, which are presently in use, the pivot arm of the picking device is driven by a cam without accumulation of the energy required for the pick in an energy accumulator.
Picking devices with storage of the energy required to move the shuttle have been disclosed in German Patent No. 30 819 and German Patent No. 47 088 where tension springs made of steel are employed.
In German Patent No. 822 827, a picking device is disclosed where the energy set free in decelerating the shuttle is stored and reused for driving the shuttle.
A picking device of the generic type is disclosed in German Patent Publication No. 27 42 088. The cam is supported for free rotation and is driven by a one-way drive clutch. Due to a descending curve portion the cam leads relative to the drive shaft within a coupling cycle as the energy for the picking motion is released. By a return motion stop means the return motion of the cam within the coupling cycle is avoided. This picking device offers an advantage over a picking device where the impact lever is driven directly by a cam, without interposed energy storage, up to product widths of only six meters.
In a Sulzer loom disclosed in the book "Weberei" by J. Schneider, Springer-Verlag 1961, the torsion bar is tensioned by way of a toggle lever stretched by a cam which is driven by the main shaft of the loom. The end of the toggle lever remote from the torsion bar is connected to the loom frame through a shock absorber.
In practice, it has become obvious that by the acceleration of the pivot arm, of the energy accumulator (spring) and the elements of the cam drive, and by friction in the picking device, about 4/5 of the accelerating energy released by the energy accumulator is lost. Furthermore, it must be borne in mind that the energy accumulator may release only 54% of the stored energy in the acceleration phase.